An existing medium caching mechanism mainly employs a dual-power or single-power drive mode, especially the single-power drive mode, and is generally composed of one drive roll and two driven rolls, or is composed of one drive roll and one driven roll.
As shown in FIG. 1, taking one drive roll 11 and two driven rolls as an example, in the existing medium caching mechanism, a driving motor 10 is fixedly mounted on a side plate 9 thereof, a first rotary shaft 13 and a second rotary shaft 12 are rotatably mounted on the side plate 9 through a second one-way bearing 15. The driving motor 10 is mounted on a b-side of the side plate 9 (for convenience of description and distinguish, the two sides of the side plate 9 are defined as a-side and b-side), a shaft of the driving motor has extension portions on both the a-side and b-side of the side plate 9. The drive roll 11 is sleeved outside the driving motor 10 and is fixedly mounted on one end of the rotating shaft of the driving motor; at the a-side of the side plate 9, a third synchronous pulley 1 is fixedly mounted on the other end of the rotating shaft of the driving motor, rotation of the driving motor 10 can directly drive the drive roll 11 and the third synchronous pulley 1 to rotate.
A first synchronous pulley 5 and a second synchronous pulley 7 are rotatably mounted to the first rotary shaft 13 and the second rotary shaft 12 respectively through a first one-way bearing 6. The three synchronous pulleys are connected with each other by a synchronous belt 3, so that the rotation pace and rotation direction thereof are consistent, the operating forces of the first one-way bearing 6 and the second one-way bearing 15 have opposite directions.
A first driven roll 4 and a second driven roll 8 are rotatably mounted on the first rotary shaft 13 and the second rotary shaft 12 respectively through a torque limiter 14, under the action of the torque limiter 14, when there is a relative rotation or a trend of relative rotation between the driven roll and the rotary shaft corresponding to it, there will exist a torque which is not larger than a set value of the torque limiter 14, this torque can prevent the driven roll from rotating or drive the driven roll to rotate. The two driven rolls are respectively windingly fitted with a tape 2 of a proper length, the other ends of the tapes 2 are both disposed on the drive roll 11.
During feeding of banknotes, when the driving motor 10 drives the third synchronous pulley 1 and the drive roll 11 to rotate forwardly, the first one-way bearing 6 slides idly, the first synchronous pulley 5 and the second synchronous pulley 7 have no effect on the first rotary shaft 13 and the second rotary shaft 12, and the second one-way bearing 15 performs lock-rotation, the first rotary shaft 13 and the second rotary shaft 12 generate a torque preventing the first driven roll 4 and the second driven roll 8 from rotating through the torque limiter 14, the drive roll 11 pulls the first driven roll 4 and the second driven roll 8 to rotate forwardly through the tapes 2 by overcoming the torque of the torque limiter 14. At this time, the linear speeds of the drive roll 11, the tape 2 and the driven rolls are maintained consistent.
Generally, during withdrawing of banknotes, the tape 2 is definitely wounded on the drive roll 11, when the driving motor 10 drives the third synchronous pulley 1 and the drive roll 11 to rotate reversely, the drive roll 11 releases the tape 2, the third synchronous pulley 1 drive the first synchronous pulley 5 and the second synchronous pulley 7 to rotate reversely by large transmission ratio, the second one-way bearing 15 rotates idly, the side plate 9 has no effect on the first rotary shaft 13 and the second rotary shaft 12, and the first one-way bearing 6 performs lock-rotation, the first synchronous pulley 5 and the second synchronous pulley 7 have effects on the first rotary shaft 13 and the second rotary shaft 12, thereby driving the first rotary shaft 13 and the second rotary shaft 12 to rotate reversely, the first rotary shaft 13 and the second rotary shaft 12 drive the first driven roll 4 and the second driven roll 8 to rotate reversely through the torque limiter 14 in a way that the first rotary shaft 13 and the second rotary shaft 12 slide with respect to the first driven roll 4 and the second driven roll 8 and thereby generating a constant torque, the first driven roll 4 and the second driven roll 8 rotate reversely and thereby tightening the tape 2 released by the drive roll 11. At this time, the linear speeds of the drive roll 11, the tape 2 and the driven rolls are maintained consistent.
In a control principle of the above mechanism, during feeding of banknotes, once the drive motor 10 stops rotating rapidly, the drive roll 11 will be affected by the brake torque of the driving motor 10, and is stopped by rapidly decelerating; a driven roll rotates with a speed that is decelerated till it stops due to a torque provided by the torque limiter 14 in a direction opposite to the motion direction. During the time within which the drive roll 11 is stopped, the rotating distance of the driven roll is larger than the rotating distance of the drive roll 11, resulting that the tape 2 can not be tensioned, and thereby affecting the next banknotes feeding.
There is an urgent demand for the person skilled in the art to solve the technical problem that during banknotes feeding, how to ensure that the tape still can remains in a tensioned state after the driving motor stops rotating.